[PATCH net 2/7] xsk: drain continuation descs after overflow in xsk_build_skb()
From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Date: 2026-06-23 13:33:23
Also in:
bpf
Subsystem:
networking [general], the rest, xdp sockets (af_xdp) · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Magnus Karlsson, Maciej Fijalkowski
From: Jason Xing <kernelxing@tencent.com> When a multi-buffer packet exceeds MAX_SKB_FRAGS and triggers -EOVERFLOW, only the current descriptor is released from the TX ring. The remaining continuation descriptors of the same packet stay in the ring. Since xs->skb is set to NULL after the drop, the TX loop picks up these leftover frags and misinterprets each one as the beginning of a new packet, corrupting the packet stream. Fix this by adding a drain_cont flag to xdp_sock. When overflow occurs and the dropped descriptor has XDP_PKT_CONTD set, the flag is raised, so we have a chance to examine and handle the potential remaining descs of this big overflow'ed skb. When the last fragment (without XDP_PKT_CONTD) is processed, the flag is cleared and the loop continues to process subsequent descriptors with the remaining budget. This behavior follows how previous xmit path treats overflow packets. Closes: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/ (local) Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path") Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> # wrapped cq addr submission onto routine Signed-off-by: Jason Xing <kernelxing@tencent.com> --- include/net/xdp_sock.h | 1 + net/xdp/xsk.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+)
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index ebac60a3d8a1..8b51876efbed 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h@@ -80,6 +80,7 @@ struct xdp_sock { * call of __xsk_generic_xmit(). */ struct sk_buff *skb; + bool drain_cont; struct list_head map_list; /* Protects map_list */
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index a7a83dc4546a..e80c035a7af5 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c@@ -737,6 +737,19 @@ static void xsk_cq_submit_addr_locked(struct xsk_buff_pool *pool, spin_unlock_irqrestore(&pool->cq_prod_lock, flags); } +static void xsk_cq_submit_addr_single_locked(struct xsk_buff_pool *pool, + struct xdp_desc *desc) +{ + unsigned long flags; + u32 idx; + + spin_lock_irqsave(&pool->cq_prod_lock, flags); + idx = xskq_get_prod(pool->cq); + xskq_prod_write_addr(pool->cq, idx, desc->addr); + xskq_prod_submit_n(pool->cq, 1); + spin_unlock_irqrestore(&pool->cq_prod_lock, flags); +} + static void xsk_cq_cancel_locked(struct xsk_buff_pool *pool, u32 n) { spin_lock(&pool->cq->cq_cached_prod_lock);
@@ -1063,11 +1076,22 @@ static int __xsk_generic_xmit(struct sock *sk) goto out; } + if (unlikely(xs->drain_cont)) { + xsk_cq_submit_addr_single_locked(xs->pool, &desc); + + xs->tx->invalid_descs++; + xskq_cons_release(xs->tx); + xs->drain_cont = xp_mb_desc(&desc); + continue; + } + skb = xsk_build_skb(xs, &desc); if (IS_ERR(skb)) { err = PTR_ERR(skb); if (err != -EOVERFLOW) goto out; + if (xp_mb_desc(&desc)) + xs->drain_cont = true; err = 0; continue; }
--
2.43.0